As data storage density continues to increase in various types of optical data storage devices, such as optical tape and optical disk drives, it is increasingly more important to provide repeatable and accurate positioning of the optical head to reliably read and write data. As such, high performance tracking servo subsystems are needed to control movement of the optical head and focus the optical beam over desired target locations on the optical media to reliably write or read the data at a particular location.
As with various types of control systems, the frequency bandwidth of the controller directly impacts the system response to various types of disturbances that may be encountered during operation. In an optical data storage device, the frequency bandwidth of the positioning or tracking servo subsystem directly impacts the ability of the optical head to track the location of the targeted data in the presence of wide band media and mechanical disturbances. As such, improving the bandwidth of the positioning or tracking subsystem may reduce data read/write errors and/or allow increased data storage density.